US3553602A - Temperature stabilized piezoelectric crystal transducer and oscillator - Google Patents

Temperature stabilized piezoelectric crystal transducer and oscillator Download PDF

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Publication number
US3553602A
US3553602A US740691A US3553602DA US3553602A US 3553602 A US3553602 A US 3553602A US 740691 A US740691 A US 740691A US 3553602D A US3553602D A US 3553602DA US 3553602 A US3553602 A US 3553602A
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United States
Prior art keywords
crystal
temperature
transducer
oscillator
frequency
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Expired - Lifetime
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US740691A
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English (en)
Inventor
Charles F Brothers
Thomas R Parkhill
Norman E Rosinski
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Applied Biosystems Inc
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Perkin Elmer Corp
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
    • G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
    • G01B7/06—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness
    • G01B7/063—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness using piezoelectric resonators
    • G01B7/066—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness using piezoelectric resonators for measuring thickness of coating
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
    • G01K7/32—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using change of resonant frequency of a crystal

Definitions

  • This invention relates to piezoelectric crystal transducers and more particularly to such transducers as are used in crystal oscillator circuits as frequency controllers, microbalances, or environmental condition (pressure, moisture, etc.) sensors and to methods for their operatron.
  • Another object of the present invention is to provide an improved crystal transducer of the above character which has a linear frequency response with respect to temperature over a significantly larger range of temperatures than heretofore possible.
  • Another object of the invention is to provide a crystal transducer of the above character which can be utilized in an oscillator circuit to provide a highly sensitive temperature measuring device.
  • Another example of the use of the present invention relates to temperature sensing device in which direct use is made of the linear temperature response for the purpose of measuring temperature changes.
  • a temperature measuring device is disclosed in which the outputs of unbalanced crystal transducer circuits of the present invention are combined to produce a difference frequency which increases linearly as a function of temperature change.
  • FIG. 1 is a schematic illustration, partially in block diagram form, of apparatus including a crystal transducer and oscillator circuit constructed in accordance with the invention.
  • FIG. 2 is a set of graphs depicting frequency versus temperature behavior for various crystals used in the apparatus of FIG. 1.
  • FIG. 4 is a schematic illustration partly in block diagram form of temperature sensing apparatus using crystal transducers and oscillator circuits constructed in accordance with the invention.
  • FIG. 1 there is shown the general arrangement of crystal transducer and oscillator circuit of the invention which consists of a crystal transducer 10 which supports a generally planar crystal 12 between support blocks 14, 15. These blocks also serve the function of electrical connectors to film electrodes 16, 17 formed on the lower and upper faces of crystal 12 and are therefore electrically insulated from each other by a suitable means such as an insulating layer 18. Blocks 14, 15 are connected by suitable conductor means such as coaxial cable 20 to an oscillator circuit 22 whose operating frequency is determined by the resonant frequency of oscillation of the crystal 12. A counter 24 or other suitable readout device such as an oscilloscope, is connected to the oscillator output to indicate changes in the output frequency.
  • suitable conductor means such as coaxial cable 20
  • oscillator circuit 22 whose operating frequency is determined by the resonant frequency of oscillation of the crystal 12.
  • a counter 24 or other suitable readout device such as an oscilloscope, is connected to the oscillator output to indicate changes in the output frequency.
  • Block is thermally coupled, as by being wrapped, to piping 26 which is connected to a source 28 of fluid at a predetermined reference temperature to thereby maintain it at reference temperature.
  • the lower end of block 15 is in direct thermal contact with peripheral portions of the surface 30 of crystal 12 and thereby serves to maintain that surface at the reference temperature.
  • Crystal 12 is preferably an AT cut quartz type adapted to vibrate in the third overtone shear mode wherein vibrations are localized in a central region. Accordingly, block 15 is provided With a recess 32 above the central region of surface 30 and block 14 is provided with an aperture 34 which exposes a substantial portion of the other surface 36, recess 32 and aperture 34 serving to provide a mounting in which the overtone vibration is unimpeded while the crystal is adequately mounted and its upper surface 30 is in a thermally controlled environment.
  • the exposed surface can serve as the monitoring surface for incident heat (by radiation, for example) as well as the monitoring face for surface loading effects such as vacuum deposits of mass.
  • the transducer 10 can be used in applications Such as thin film thickness measurement, water vapor monitoring, microbalance studies of surface physics, and many others. In these applications the temperature of the surface 36 takes values which approach that of the environment to which it is exposed and, in general, a temperature gradient is developed across the crystal.
  • This temperature gradient is found to produce a linear change in the frequency of operation of the crystal transducer and permits the construction of an oscillator circuit which can be used as a directly calibrated device either for temperature measurement or for measurements of other physical phenomenon to which the exposed surface may be sensitive with negligible or easily applied temperature compensation.
  • the solid graphs or lines 38a, b, 0 represent the frequency temperature functions for the corresponding crystal cuts using temperature difference technique. It is easily seen that these functions have straight line character with uniform slope and represent linear relationship between the temperature and frequency variables. Thus, although the crystals behave in the classical nonlinear manner and according to the well known family of S-curves when heated uniformly, they are found to follow a linear law when heated differentially with a temperature gradient. It is also found that the angle or slope of the lines 38a-d with respect to the temperature axis is a function of the original angle of cut of the crystal and, to that extent, crystal cuts with a high degree of temperature sensitivity or nearly negligible temperature sensitivity (under a temperature gradient) are found to exist.
  • Means including a cylindrical plunger 54 having a shallow recess 55a at one end 55 is captured in region 46 so that end 55 is urged toward the surface 56 of crystal 52 to engage the periphery thereof but to leave the central portion of surface 56 free to vibrate Within recess 55a.
  • the plunger is made of aluminum and is provided with an insulating layer on its lateral surface 58 to electrically insulate it from the remainder of housing 41.
  • the other end of plunger 54 is provided with a well 60 into which a spring 62 is seated and held with a set screw 64.
  • Means is provided for maintaining a controlled temperature at the inner surface 56 of the crystal 52 and includes tubing 70 which encircles base 42 and is, for example, made of thermally conductive metal such as copper and is silver soldered within an annular recess 72 formed about base 42.
  • Tubing 70 is connected to a suitable source of fluid which is maintained at a predetermined temperature suitable for establishing the reference temperature on crystal face 56.
  • the transducer of FIG. 3 can be used in the circuit of FIG. 1 as a probe or other sensing transducer to measure temperature or mass deposits.
  • mass deposits it is desirable to eliminate the effects of temperature as much as possible and this is achieved by selecting a cut of crystal for which the linear response to differential temperature across the crystal has a slope as near to zero as possible.
  • a large slope is desirable in order to provide greater sensitivity.
  • FIG. 4 illustates a circuit utilizing a pair of transducers of the type shown in FIG. 3 and which utilizes their properties to produce an audio output frequency which is directly related t the variable being measured.
  • a first oscillator circuit including crystal transducer 82 connected to an oscillator 84 and a second oscillator circuit 86 including a crystal transducer 88 connected to oscillator 90.
  • Both crystal transducers 82, 88 are connected to a common temperature source 92 which serves to establish a reference temperature for both of the transducers.
  • the outputs of oscillators 84 are fed into the inputs of suitable mixer stage 94 where in they are heterodyned to produce an output difference frequency which is directly investigated or converted to DC by a readout stage 96.
  • transducer 82 has a slope of 2 p.p./C. while oscillator 88 has a response of +2 ppm/C.
  • the output frequencies of the oscillators will diverge, and, when mixed, will produce a difference frequency at stage 94 which is in the audiofrequency range having a sensitivity of about 4 p.p.m./ C.
  • a change in temperature of about 0.05 C. is detected for a difference of one cycle per second in frequency.
  • the same general scheme shown in FIG. 4 can also be used to produce a temperature insensitive device by selecting both of the crystals to have approximately the same temperature sensitivity. That is to say, each could be selected to have a sensitivity of -2 p.p.m./ C. If the exposure aperture 82a of crystal transducer 82 is masked to prevent the deposits thereon while the other aperture 88a is exposed to the, environment, the output audiofrequency will reflect only the change in vibrating frequency of the exposed crystal and the effect caused by changes in temperature which may have been encountered will be balanced out or cancelled because both crystals are linearly affected in the same way.
  • a method of causing the operating frequency of a crystal controlled oscillator to vary linearly with temperature comprising the steps of maintaining one surface of the crystal of said oscillator at a predetermined temperature while simultaneously varying the temperature of the other surface to cause a temperature gradient to develop between the crystal surfaces, said temperature gradient being varied as said temperature on said second surface is varied thereby causing a frequency shift in the operating frequency of said crystal controlled oscillator which varies linearly as a function of said varying temperature gradient.
  • a crystal transducer for use in an oscillator circuit comprising a crystal, means for supporting said crystal while permitting the same to vibrate and including an aperture for exposing one surface of said crystal to an environmental condition to sense the same, means making electrical connections to the electrically operative surfaces of said crystal, means for maintaining another surface of said crystal at a predetermined reference temperature whereby a temperature gradient is developed across portions of said crystal, said gradient thereby causing a linear frequency shift of its natural operating frequency with respect to changes in said temperature gradient.
  • a crystal transducer as in claim 2 wherein said crystal comprises an AT cut quartz plate having opposed generally parallel surfaces between which said temperature gradient is developed.
  • first and second crystal controlled oscillator circuits including first and second crystal transducers, each of said transducers comprising a crystal having active surfaces including certain surfaces adapted to be connected to an electrical circuit, means for supporting said crystal while permitting the same to vibrate and including an aperture for selectivcly exposing at least one surface of said crystal to an environmental condition to sense the same, means for making electrical connections to the electrically active surfaces of each of said crystals, means for maintaining at least one surface of said crystals at a predetermined reference temperature, temperature gradients being developed across said crystal causing linear frequency shifts in its natural oprating frequency with respect to changes of said temperature gradient, a mixer stage having inputs for receiving the output of each of said first and second oscillator circuits, said mixer stage serving to heterodyne said oscillator output signals to produce a difference fre quency indicative of differences in the environmental condition to which each of said crystals is exposed.
  • each of said first and second crystals are selected to have the same temperature dependence, one of said crystals being selectively exposed to an environment to be measured while the other crystal is subjected only to the temperature condition of said environment whereby effects of temperature are cancelled out from the output of said mixer stage.
  • Crystal controlled sensing apparatus as in claim 6 wherein said first and second crystals are selected to have gradient temperature sensitivity of differing slope so that exposure of said surfaces of said crystals to an environmental temperature condition differing from said reference temperature produces a linear divergence in the output of said oscillator circuits which is directly roportional to the temperature difference between said reference temperature and the temperature of said environment.
  • a crystal oscillator transducer comprising a piezo electric, generally planar crystal having first and second spaced surfaces, a housing including means therein for supporting said crystal by one surface thereof and for making electrical contact therewith, said housing having an aperture therein for exposing said one surface of said crystal to an external environment for sensing the same, means for urging the other surface of said crystal into engagement within the means for supporting said first surface to form a mounting therewith in which said crystal is permitted to vibrate, said last named means including means for making electrical contact with said other surface of said crystal, means for electrically isolating said housing and said urging means, means for maintaining said other surface of said crystal at a predetermined temperature while permitting the temperature of said exposed surface to vary with the environment to which it is exposed.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
  • Measuring Fluid Pressure (AREA)
  • Oscillators With Electromechanical Resonators (AREA)
US740691A 1968-06-27 1968-06-27 Temperature stabilized piezoelectric crystal transducer and oscillator Expired - Lifetime US3553602A (en)

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US74069168A 1968-06-27 1968-06-27

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US (1) US3553602A (de)
DE (1) DE1931883A1 (de)
GB (1) GB1229505A (de)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3723778A (en) * 1972-02-07 1973-03-27 Inficon Inc Thickness sensor for sputtering systems utilizing magnetic deflection of electrons for thermal protection
US4079280A (en) * 1976-06-02 1978-03-14 Hewlett-Packard Company Quartz resonator cut to compensate for static and dynamic thermal transients
US5004987A (en) * 1989-05-19 1991-04-02 Piezo Crystal Company Temperature compensated crystal resonator found in a dual-mode oscillator
US5041800A (en) * 1989-05-19 1991-08-20 Ppa Industries, Inc. Lower power oscillator with heated resonator (S), with dual mode or other temperature sensing, possibly with an insulative support structure disposed between the resonator (S) and a resonator enclosure
US5179028A (en) * 1990-04-20 1993-01-12 Hughes Aircraft Company Antibody coated crystal chemical sensor
US5803099A (en) * 1994-11-14 1998-09-08 Matsumura Oil Research Corp. Ultrasonic cleaning machine
US5836691A (en) * 1996-07-17 1998-11-17 Techno Togo Limited Company Method of thermometry and apparatus for the thermometry
US20120187983A1 (en) * 2011-01-20 2012-07-26 Taiwan Semiconductor Manufacturing Company, Ltd. Frequency generator

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3732594A1 (de) * 1987-09-28 1989-04-06 Leybold Ag Einrichtung zum ermitteln der jeweiligen dicke von sich veraendernden material-schichten auf einem substrat
DE29621925U1 (de) * 1996-12-17 1997-02-20 Nedcon Magazijninrichting B.V., Doetinchem Bremsrolle, insbesondere zum Einbau in eine geneigte Rollenbahn

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3723778A (en) * 1972-02-07 1973-03-27 Inficon Inc Thickness sensor for sputtering systems utilizing magnetic deflection of electrons for thermal protection
US4079280A (en) * 1976-06-02 1978-03-14 Hewlett-Packard Company Quartz resonator cut to compensate for static and dynamic thermal transients
US5004987A (en) * 1989-05-19 1991-04-02 Piezo Crystal Company Temperature compensated crystal resonator found in a dual-mode oscillator
US5041800A (en) * 1989-05-19 1991-08-20 Ppa Industries, Inc. Lower power oscillator with heated resonator (S), with dual mode or other temperature sensing, possibly with an insulative support structure disposed between the resonator (S) and a resonator enclosure
US5179028A (en) * 1990-04-20 1993-01-12 Hughes Aircraft Company Antibody coated crystal chemical sensor
US5803099A (en) * 1994-11-14 1998-09-08 Matsumura Oil Research Corp. Ultrasonic cleaning machine
US5836691A (en) * 1996-07-17 1998-11-17 Techno Togo Limited Company Method of thermometry and apparatus for the thermometry
US20120187983A1 (en) * 2011-01-20 2012-07-26 Taiwan Semiconductor Manufacturing Company, Ltd. Frequency generator

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Publication number Publication date
GB1229505A (de) 1971-04-21
DE1931883A1 (de) 1970-01-08

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